In recent years, a fuel is used in which alcohol is added to gasoline, so that there has been an ardent need for a technology of increasing an alcohol concentration. Alcohol can be produced at a lower cost by fermenting an organic material, for example, corn. However, biomass alcohol produced in such a method is of a lower concentration, and such alcohol has to be treated for its higher concentration by separating water content from the alcohol. In order to separate the water content from the alcohol to obtain a higher concentration, there is used a method of distillation. This method, however, suffers a disadvantage that energy consumption becomes larger. When a great amount of energy is consumed in treating alcohol for its higher concentration, it becomes impossible or difficult to reduce total consumption of gasoline even though alcohol-added gasoline is combusted.
The present inventor developed a separating apparatus for increasing an alcohol concentration by way of lower energy consumption (See Patent Document 1).
Patent Document 1: JP-A-2001-314724
In this separating apparatus, an atomization chamber of a closed structure is filled with an alcohol solution, the alcohol solution in this atomization chamber is ultrasonically vibrated by an ultrasonic vibrator to be atomized into mists, and such atomized mists are condensed and collected, so that an alcohol solution of a higher concentration can be separated. This separating apparatus is capable of separating highly concentrated alcohol as a target substance in the following operation.
Alcohol is easier than water to be shifted to the surface of a solution, and the alcohol concentration is higher in the solution at the surface. In this state, when the solution is subjected to an ultrasonic vibration, the highly concentrated alcohol turns to mists to be released into the air in a state of fine particles under the effect of the energy generated by the ultrasonic vibration. The mists released into the air have a higher concentration of alcohol. This is because the solution at its surface side with a higher alcohol concentration is easier to be transformed into the mists. The fact that alcohol is easier to be vaporized than water also accelerates a higher concentration of alcohol in the mists. This is because a greater amount of alcohol is vaporized than water out of the mists of alcohol solution, so that alcohol concentration becomes higher which is contained in a carrier gas. Consequently, when the atomized mists which are contained in the carrier gas and a component which is vaporized from the mists, namely, the mist component are collected from the carrier gas, a highly concentrated alcohol solution is to be separated. In this method, a highly concentrated alcohol solution can be separated without subjecting the solution to heat. For this reason, it is possible to separate a target substance of a high concentration with lower energy consumption. The method also carries the advantage that the target substance can be separated without undergoing deterioration because there is no heating.